The embodiments described herein relate to an X-ray CT (Computed Tomography) apparatus.
In general, an X-ray CT apparatus generates X-rays with a desired energy spectrum by controlling an X-ray tube voltage of an X-ray tube. There is also a known technique for obtaining a tomographic image based on CT values obtained using X-rays with an energy spectrum generated from an X-ray tube using a higher X-ray tube voltage and those obtained using X-rays with an energy spectrum generated from the X-ray tube using a lower X-ray tube voltage, as disclosed in Japanese Patent Application Laid Open No. 2004-065975, for example. More particularly, the technique includes a technique of obtaining a weighted subtraction image in which a certain material within a subject is enhanced using the fact that X-ray absorption coefficients of materials within the subject are different from one another in response to different energy spectra of X-rays. A technique of obtaining a CT image using projection data based on X-rays with two different energy spectra is sometimes referred to as dual energy imaging.